A temperature-measuring device with a dual temperature sensor is known from DE 101 39 705 A1. In the prior-art dual temperature sensor, two temperature sensors are arranged on opposite sides of a sensor housing, thermally insulated from one another. One of the temperature sensors is directly in contact with the surface of the patient's skin, while the other temperature sensor measures the temperature in the environment. The dual temperature sensor can be attached to the skin in different ways. In case of temperature measurements on the head, a head band made of an elastic material, which can be adapted to the shape of the head especially well, is suitable. The dual temperature sensor is frequently attached with adhesive strips in case of temperature measurements in the abdominal region. The manner of attaching also depends on the patient's physical activity.
If the dual temperature sensor is not arranged properly or if there is increased physical activity, it may happen that the dual temperature sensor separates from the skin surface and the temperature measurement is interrupted. The falling off of the dual temperature sensor from the skin surface must be indicated in a short time in case of medical applications in order for the interruption of the measured data acquisition to be limited to the absolute minimum. This is especially important when the temperature is used as a parameter for a temperature or heating output regulation.
Various function indicators are known for indicating the contact of a sensor with the skin surface. Thus, an additional optical sensor, which detects the change in the position of the dual temperature sensor in relation to the skin surface, can be used.
In a device known from U.S. Pat. No. 5,732,711, the skin temperature is measured with two temperature sensors arranged adjacent to one another. The processed measured temperature signals are compared with one another by forming the difference, and the exceeding of a predetermined limit value of the temperature difference is used as an indicator for a temperature sensor that is no longer in contact with the skin surface. The prior-art monitoring device is suitable for certain sensor designs only, and an additional temperature sensor is needed for the monitoring only.